A semiconductor device using a wide-gap semiconductor such as gallium nitride (GaN), silicon carbide (SiC), and diamond is more excellent in important characteristics such as breakdown voltage, electron mobility, and thermal conductivity than a semiconductor device using silicon (Si). Especially, in an HEMT (High Electron Mobility Transistor) having an AlGaN/GaN heterostructure as one form of a semiconductor device using GaN, an excellent radio frequency characteristic and low on-resistance can be achieved since the HEMT has high electron mobility and a high carrier density.
In such a wide-gap semiconductor, a substrate such as a wafer is used in which a wide-gap semiconductor is epitaxially grown on an Si substrate, which is inexpensive and easy to have a large diameter. In a case where a GaN-based material is to be epitaxially grown on an Si substrate, for example, lattice mismatch between Si and the GaN-based material is as much as 17 to 19%. When the lattice mismatch is large, a warping amount of the substrate increases.
In a semiconductor device, it is important to control warping of the substrate and improve a manufacturing yield.